A new survey of U.S. millionaires reveals that $1 million in net worth is not nearly enough to make them feel financially secure.

In fact, according to UBS Investor Services, most of the millionaires responding to a survey say their life has them "stuck on a treadmill they can't get off" just to maintain their current standard of living.

In fact, it's not until they're worth $5 million or more that most believe they have enough to feel financially secure.

"Many millionaires, particularly those with children at home, feel pressure to keep working hard to improve or just maintain their family's lifestyle," UBS says after surveying 2,214 U.S. millionaires from March 11-19 of this year. It followed up the survey with 90 in-person interviews.

To make matters worse, 63 per cent of working millionaires who responded believe that one major setback, such as lost job or a market crash, would have a major impact on their lifestyle.

They can't give up their jobs or work part-time as they might want to, because of fear of falling behind, the study found.

"Half of these millionaires feel stuck on a treadmill where slowing down at work would mean giving up the lifestyle to which the whole family has grown so accustomed," UBS wrote in its analysis.

In further proof that millionaires are just as stressed as the rest of us:

  • 65 per cent worry their children don't understand the value of money.
  • 54 per cent worry about their children lacking motivation.
  • 63 per cent worry about growing wealth inequality.
  • 71 per cent worry the dream of upward mobility is fading in America.

Of the group surveyed, 30 per cent said they were born into working-class families and another 42 per cent said they grew up in middle-class households.